J.R.R. Tolkien based the fictional language Quenya mainly on Finnish.
Quenya is one of the major Elvish languages in Tolkien’s legendarium. He developed it as a formal, ancient language associated especially with the High Elves, and its sound patterns and grammar were strongly influenced by Finnish. Tolkien also drew on Latin and Greek, while creating an independent linguistic system with its own history and regional forms.
Sindarin is another major Elvish language, but Tolkien based much of its structure and sound on Welsh rather than Finnish. This distinction is a frequent source of confusion because both languages appear in The Lord of the Rings and The Silmarillion. Quenya names include Eärendil and Galadriel, while the title of the poem “Namárië” is Quenya.
Tolkien was a philologist, and his languages were built with historical development, sound change, and relationships between related tongues rather than as collections of random words.